Comprehensive study of the resistivity of copper wires with lateral dimensions of 100 nm and smaller

Abstract

Copper wires were prepared in a silicon oxide matrix using the methods of semiconductor manufacturing and were electrically characterized. The width of the smallest structure was 40 nm and of the largest, 1000 nm; the heights were 50, 155, and 230 nm. Many samples of each size have been measured in order to perform a systematic investigation. The resistivity of the sample was extracted using the temperature coefficient of resistance. A significant increase in the resistivity was found for the small structures (roughly a factor 2 for 50-nm width). A model based on physical parameters was used in the analysis of the electrical data and very good agreement was obtained. The sensitivity of the various model parameters obtained by a best-fit procedure to the experimental data has been investigated. The impact of width and height on the resistivity, the influence of electron scattering at grain boundaries compared to surface scattering, and the impact of grain sizes and impurities will be discussed in detail.

Line Scaling Effect on Grain Structure for Cu Interconnects

“…Extensive data have been published [1][2][3][4] on the microstructure of damascene Cu lines regarding the grain texture and size distribution and their variations with different line widths. Nevertheless, only few results have been reported recently [5][6][7][8] on the microstructures of Cu lines narrower than 100 nm. For ultra-narrow Cu lines less than 100 nm wide, the resistivity was found to increase as the line width scales down.…”

Dual capacitive-inductive nature of periodic graphene patches: Transmission characteristics at low-terahertz frequencies

“…The different physical behavior of these two materials is due to the fact that τ m τ g . If electron scattering is effective, ωτ 1, which is not true for graphene in the low THz assuming its typical long mean-free path but which is satisfied in this frequency range by typical metals at room temperature (e.g., at 1 THz, ωτ m 0.13; even smaller τ m values will likely result due to enhanced surface and grain-boundary scattering in thin metal sheets, 41 which would even more forcefully satisfy the inequality), then…”

“…The resulting surface impedance is Z g s = 1/σ g = 474.3 + j 1490.1 . For metal at the same temperature and frequency, σ m = (32.7 − j 4.1)d mS, where d is measured in nm, assuming typical parameters n e = 5.9 × 10 28 m −3 and τ m = 20 fs (this value would be smaller for thin metal sheets due to surface and grain-boundary scattering 41 …”

Structural Response of Nano-scale Damascene Copper Lines to Annealing

“…1,2 This effect is conventionally attributed to electron scattering on sidewalls as well as on grain boundaries because grain size in such interconnects is expected to approach the mean electron free path (³40 nm at ambient temperature). An obvious way to minimize this problem is use of an appropriate annealing process which allows production of reasonably coarse-grained structures.…”